The Department of Homeland Security released a report showing that apprehensions of undocumented immigrants at the U.S.-Mexico border are at their lowest level since 1973, leaving many observers contemplating the factors responsible for this decline. New data from a research team led by Wayne Cornelius, Director of the Center for Comparative Immigration Studies at the University of California, San Diego, sheds light on the decline in apprehensions and reveals the surprising, unintended consequences of border enforcement.